Scalable and tileable holographic displays

ABSTRACT

A holographic display system for generating a super hologram with full parallax in different fields of view in the horizontal and vertical directions. The display system includes assemblies or subsystems each adapted to combine holographic displays and coarse integral displays to produce or display a coarse integral hologram. The display system is adapted to combine such displays or display systems to add more detail or information. For example, the display system can be assembled as if it were made up of “holographic bricks” that can be stacked and combined to provide a unique image/output. Briefly, the display system described herein teaches techniques for combining coarse integral holographic (CIH) displays in a seamless and scalable manner, e.g., a display system where multiple spatial light modulators (SLMs) can be placed or provided behind coarse integral optics.

BACKGROUND

1. Field of the Description

The present invention relates, in general, to autostereoscopic displaysand to holography and to holographic displays, and, more particularly,to displays adapted to facilitate scaling and tiling (or otherwisecombining) such holographic displays, e.g., scalable and tileable coarseintegral holographic displays.

2. Relevant Background

Holography is a technique that enables three-dimensional (3D) images tobe generated, recorded, and later displayed. It typically involves theuse of a laser, interference, diffraction, light intensity recording,and suitable illumination of the recording. The image changes as theposition and orientation of the viewing system changes in exactly thesame way as if the object were still present, thereby making the imageappear in 3D. The holographic recording itself is not an image as it ismade up of an apparently random structure of varying intensity, density,or profile.

As the demand for 3D displays rapidly grows, holographic displays areconsidered by many within the 3D entertainment industry as the ultimategoal of 3D displays. Such high regard is held for these devices becauseholographic displays are capable of displaying all the 3D cues of a realscene to a viewer. Unfortunately, to date, designing and fabricatingholographic displays have proven difficult due to one or more challengesthat have limited display size, field of view, frame rate, and/orprevented providing both horizontal and vertical parallax.

In this regard, to create a large holographic display with a wide fieldof view (fov), the pitch of the display's spatial light modulator (SLM)must be fine (e.g., less than 1 micrometer (μm) and more typically lessthan 0.5 μm for an approximately 30° fov) over a large area (e.g., 127millimeters (mm) by 100 mm or the like). Unfortunately, the pitches ofcommon SLMs, such as digital mirror devices (DMDs) or liquid crystal onsilicon (LCOS) devices, are typically only as coarse as about 5 to 10 μmand are the same horizontally and vertically, providing only 1° to 3°fov. Further, the pitches are only maintained over small areas in thesedevices such as over 20 mm by 20 mm. Demagnifying optics can be used toincrease the pitch and field of view but at the generally unacceptableexpense of the image size (and vice versa) due to the Lagrange Invariant(i.e., for an optical system of only lenses, the product of the imagesize and ray angle is constant).

In some attempts to provide an improved holographic display, multipleSLMs have been tiled together to increase either the size or field ofview of the hologram. With simple spatial tiling of multiple SLMs toincrease the size of the hologram, however, there are noticeable seamsin the holographic image due to gaps between the SLMs from the bordersand electronics. Spatial tiling of a single SLM has also been achievedusing replication optics or using 2-axis scanners. Gaps andmisalignments in the spatial tiling appear at the hologram plane andvisually interfere with and confuse the 3D imagery. Multiple SLMs havealso been arranged in an arc, with precision optical mounts, to increasethe field of view. The holographic images overlap in the center of thearc a far distance from the SLMs, with a corresponding reduction in theholographic image's resolution the further the distance from the SLM.Several of these systems use an asymmetric diffusing screen, producinghorizontal parallax only (HPO) images. Accousto-optical modulators(AOMs) are capable of providing traveling acoustic waves of pitches ofabout 5 μm over larger lengths. These large lengths can be arranged intowidths of about 1 meter by heights of about 100 mm. However, to cancelthe motion of the traveling waves, descanning optics and scanners arerequired. Also, other optics may be required to create higher pitches atthe expense of display width. Further, the acoustic waves only diffractin one direction, and the resulting hologram is necessarily HPO.

Due to the horizontal arrangement of the human eyes, horizontal parallaxis more important than vertical parallax for binocular stereopsis andmotion parallax. This fact is often used in horizontal parallax only(HPO) holographic displays to reduce computation and data bandwidthrequirements compared to full parallax holographic displays. However,the appearance of the HPO hologram does not change with vertical motionof the viewer and their viewing location or point of view. In otherwords, a single viewer may move their head up and down or vertically(e.g., be sitting or squatting and then stand up), and the hologram'sappearance would not change as would a true 3D object. In some artisticand entertainment applications, especially those provided for singlestationary viewers, the loss of vertical parallax may be acceptable.

However, vertical parallax is important to fix absolute position inspace. In many 3D display implementations, the loss of vertical parallaxis not acceptable, which has led some experts in the 3D display industryto argue that a holographic display that is HPO is a “non-starter.” Forexample, in implementations involving interaction with the hologram orinvolving multiple viewers that collaborate (e.g., point to or interactwith the same location on the holographic image), the holographicdisplay will be ineffective unless there is at least a small amount ofvertical parallax. Such “limited vertical parallax” may be necessary forthe viewers to see or experience a consistent scene from differingpoints of view. Due to human kinetics (e.g., it is easier for humans toshift their views left and right than up and down), the amount ofdesirable vertical parallax is often much lower than a desirable amountof horizontal parallax.

Hence, there is a need for holographic displays or holographic displaysystems that address some of these challenges. Preferably, such newholographic displays would provide a relatively large 3D image orhologram and would provide some amount of vertical parallax (e.g.,provide limited vertical parallax). An issue, though, facing suchdevelopment is that providing different amounts of information andfields of view in the horizontal and vertical directions is difficultwith current full parallax holographic displays. With common squarepixel SLMs, the horizontal and vertical pitches and, therefore, thefields of view are the same (unless anamorphic optics are used, whichoften is not desirable due to astigmatic aberrations, cost,manufacturing and design complexity, and other concerns).

SUMMARY

The inventor recognized that it is desirable to implement holographicdisplays or display systems that are each adapted to combine holographicdisplays and coarse integral displays to produce or display a coarseintegral hologram. However, it is also then desirable to provide adisplay system or assembly that is useful for combining such displays ordisplay systems to add more detail or information. For example, it isdesirable to provide a display system that can be assembled as if itwere made up of “holographic bricks” that can be stacked and combined toprovide a unique image/output. Briefly, the display system describedherein teaches techniques for combining coarse integral holographic(CIH) displays in a seamless and scalable manner (e.g., a display systemwhere multiple spatial light modulators (SLMs) can be placed or providedbehind coarse integral optics).

The displays and systems may be thought of as using a method ofcombining several low pitch, small area spatial light modulators (SLMs)and/or spatially/temporally multiplexing a single SLM to form a modestlysized, wide horizontal field of view display with a small amount ofvertical parallax (e.g., providing limited vertical parallax rather thanproviding an HPO display). The horizontal and vertical informationcontent and fields of view may be adjusted separately.

The SLMs provide a set of fully holographic 3D images, but each with asmall area and a small field of view (or “fov”). Each hologram output bythe SLMs reproduces a different narrow viewpoint of the same 3D scene.The coarse integral optics angularly tiles the multiple narrow field ofview holograms into a single large field of view hologram.

More particularly, a holographic display system is provided thatincludes an array of holographic display devices each operable toprovide a plurality of holographic images of a scene from differingviewpoints of the scene. The display system also includes a periscopiccoarse integral optics assembly positioned between the array ofholographic display devices and a viewing space for the holographicdisplay system. This assembly includes a periscopic relay for each ofthe holographic display devices to relay the holographic images. Inpractice, the periscopic coarse integral optics assembly is typicallyadapted to combine the plurality of holographic images into a singlehologram viewable in a hologram image plane. In some embodiments, theholographic display devices are each a spatial light modulator operableto display one of the plurality of holographic images.

In some embodiments, the periscopic relay includes a field lens adjacentan output surface of a corresponding one of the holographic displaydevices and further includes a relay lens spaced apart from each of thefield lenses. Also, the periscopic coarse integral optics assemblyfurther includes a common transform lens proximate to the relay lensescombining the plurality of holographic images transmitted from the relaylenses. In such cases, the periscopic coarse integral optics assemblymay further include a field lens at the hologram image plane, and thenthe field lens has a height substantially equal to the height of thecommon transform lens. Further, the common transform lens has a heightsubstantially equal to the height of the array of holographic displaydevices.

According to another aspect of the description, a scanning periscopiccoarse integral holographic display is provided with a scanning relayincluding: a spatial light modulator providing elemental holograms of a3D scene; an array of field lenslets; and a scanner operable to directeach of the elemental holograms onto one of the field lenslets. Thedisplay further includes a periscopic coarse integral optics assemblypositioned between the scanning relay and a viewing space for theholographic display. This assembly includes a periscopic relay for eachof the field lenslets to relay the elemental holograms and is adapted tocombine the plurality of holographic images into a single hologramviewable in a hologram image plane.

The periscopic relay may include a field lens adjacent an output surfaceof a corresponding one of the field lenslets of the scanning relay andmay further include a relay lens spaced apart from each of the fieldlenses of the periscopic relay. In these embodiments, the periscopiccoarse integral optics assembly further may include a common transformlens proximate to the relay lenses combining the plurality ofholographic images transmitted from the relay lenses. Then, theperiscopic coarse integral optics assembly may also include a field lensat the hologram image plane. It may be useful for the field lens to havea height substantially equal to the height of the common transform lens,and then the common transform lens may have a height substantially equalto the height of the array of field lenslets in the scanning relay.

Scaling and tiling may be provided in a display assembly. Such a displayassembly may include at least two scanning relays each including: aspatial light modulator providing elemental holograms; an array of fieldlenslets; and a scanner operable to direct each of the elementalholograms onto one of the field lenslets. This display assembly also mayinclude a periscopic coarse integral optics assembly including aperiscopic relay for each of the field lenslets. Then, each of theperiscopic relays may include a field lens adjacent an output surface ofa corresponding one of the field lenslets and further include a relaylens spaced apart from each of the field lenses of the periscopic relay.

Scaling may be provided by configuring the periscopic coarse integraloptics assembly to include a common transform lens proximate to therelay lenses combining the plurality of holographic images transmittedfrom the relay lenses. Further, the periscopic coarse integral opticsassembly further includes a field lens at a hologram image plane for theassembly, and the field lens has a height substantially equal to theheight of the common transform lens.

Tiling is provided by adapting the periscopic coarse integral opticsassembly to further include a transform lens proximate to the relaylenses associated with each of the scanning relays that combines theplurality of holographic images transmitted from the relay lenses ofeach of the scanning relay. In such a display assembly, the periscopiccoarse integral optics assembly further includes a field lens at thehologram image plane, paired with each of the transform lenses. Further,the field lenses each may have a height substantially equal to theheight of a corresponding one of the transform lenses.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a coarse integral display that uses a single imagesource and scanning to provide an angularly tiled super hologram;

FIG. 2 illustrates a scaled CIH system combining two of the displays ofFIG. 1 using a common transform lens so as to provide a super hologramwith view gaps;

FIG. 3 illustrates a tiled CIH system combining two of the displays ofFIG. 2 using two transform lens positioned side-by-side to output superholograms with an image gap;

FIG. 4 illustrates relay optics using a lens pair to provide a scannedimage;

FIG. 5 illustrates relay optics configured in the form of a periscoperelay;

FIG. 6 illustrates a periscopic coarse integral array display accordingto the present description;

FIG. 7 illustrates a periscopic scanning relay that may be used within adisplay system such as that of FIG. 6;

FIG. 8 illustrates a scanning periscopic coarse integral holographicdisplay using the relay of FIG. 7 in combination with the coarseintegral array of FIG. 6;

FIG. 9 illustrates a display system providing scaling of the scanningperiscopic coarse integral holographic display of FIG. 8; and

FIG. 10 illustrates a display system providing tiling of the scanningperiscopic coarse integral holographic display of FIG. 8.

DETAILED DESCRIPTION

Briefly, the present description provides a display system that combinesholographic displays or holographic display systems (sometimes referredto herein as “coarse integral holographic (CIH) displays”) such that theCIH displays are tileable and the overall display system is readilyscalable. Generally, each of the CIH displays includes a plurality ofspatial light modulators (SLMs). The SLMs are arranged in a side-by-side(or planar) manner and may be low pitch, small area SLMs, and the CIHdisplay systems are configured with coarse integral optics (or anoptical assembly) to combine the output images or output light (i.e.,small area and small field of view (fov) holograms) from the SLMs toform a modestly sized, displayed holographic image (a single larger areahologram with a large fov) with possibly different horizontal andvertical fields of view.

A coarse integral display may include an array of SLMs providing“elemental” 2D images, a lens array, and a large transform lens. Eachelemental image in the array of 2D images is of the same scene but fromdifferent viewpoints. A lens array is placed in front of the SLMs toreceive the array of 2D images, such as with one lens centered over eachviewpoint image output from the SLM array. Each image-lens pair becomesor acts, in effect, as a narrow field of view projector, with suchprojectors' axes all being parallel in a typical implementation.

The large transform lens is selected to act or function to reimage theprojectors' images and to bend the projectors' axes so that they crossand fan outward. The 2D images are thereby angularly tiled by the opticsor coarse integral optical assembly. This produces a view-dependentimage with a wide field of view. However, the views are discrete anddiscontinuous, and each image is still 2D. An apparent 3D image may beseen, but the coarse integral display does not support accommodationcues for a reasonable number of views.

With this in mind, the SLMs of the array can be operated to provide anarray of elemental holographic displays rather than elemental 2D imagesin the coarse integral display. In this way, each element in the outputcoarse integral hologram is a narrow field of view 3D hologram thatincludes all 3D cues including stereopsis, accommodation (focus), andvergence cues. Also, and significantly, the output or produced 3Dhologram has continuous horizontal and vertical parallax. The courseintegral optics are designed to (and do act to) tile the viewpoints ofmany narrow field of view elemental holographic displays (e.g., SLMs)into a single, large field of view or “super” holographic display. Itshould also be understood that because the array of elemental 3Dholograms provided by the array of SLMs does not need to form a squarearray, the field of view in the horizontal direction may be differentfrom that of the vertical direction.

With this general understanding of a CIH display understood, it may beuseful to discuss exemplary challenges addressed with the displaysystems of the present description. One main challenge addressed by thepresent description is how to design and assemble a large holographicdisplay of arbitrary size (which may be labeled or named a “holographicwall”). Conceptually, it was thought that such a display system could beachieved using scalable and tileable component systems/displays that canbe labeled or named “holographic bricks.” Each holographic brick may bea holographic display in of itself and may include a spatial lightmodulator (SLM), optics, scanning, and, in some cases, devices forrendering, computational abilities, and connectors. Each holographicbrick likely would be scalable such as with multiple SLMs and scannersthat may be combined until each holographic brick has reached an optimalor desired field of view and/or size. Multiple holographic bricks may betiled together, e.g., seamlessly when possible or practical, to create alarge holographic display or a larger display system that may be aslarge as desired for a particular application (i.e., size is no longer alimiting factor in display system design).

As will be understood by those skilled in the arts, a holographicdisplay is unlike a projection or large screen display in that it has tomaintain a high pixel density (or pitch) even at large display sizes.The hologram's pixel pitch determines how much a light ray is bent (ordiffracted). For example, a pixel pitch of about 0.001 millimeters (mm)deflects a light ray about 30 degrees. The need for having a dense pixeldensity over the entire large display area is driven by the hologram'spattern of varying pixel pitch, which can direct and focus light tocreate a three-dimensional (3D) image with a complete set of 3D cuesincluding parallax, stereopsis, and focus.

Unfortunately, it is difficult to create a single large holographicdisplay due to the enormous amounts of information that must be computedand displayed. A space bandwidth product is a measure of the display'sinformation content related to the pixel pitch maintained over a displayarea. The space bandwidth product of current SLMs, such as a digitalmicromirror device (DMD), only allows a display that is, for example,1-inch by 1-inch with a 0.2 degree by 0.2 degree field of view (fov).

To increase the size of the display from a single SLM, one may try totake advantage of the high speed frame rate of current SLMs (e.g., a DMDmay operate at 22,500 frames per second (fps)) and a mirror scanner todistribute multiple images of the SLM. Work has been done to develop aholographic display system that uses a scanned DMD and coarse integraloptics (e.g., a lens array and a large transform lens) to create adynamic hologram. For example, FIG. 1 illustrates a CIH display (orholographic display system) 100 that is operated to provide a superhologram 150 with angularly tiled views (e.g., with crossing opticalaxes).

As shown, the CIH display 100 includes an SLM 110 and an optical relay(e.g., a 4f relay) 120 with first and second lens 122 and 124,respectively. The CIH display 100 includes a scanner 130 disposedbetween the first and second lenses 122, 124 such as at the opticalrelay's Fourier plane. The SLM 110 may be located at the front focalplan of the first lens 122, and the scanner 130 may be located at therear focal plane of the first lens 122 and at the front focal plane ofthe second lens 124. The scanned and translated SLM image 133 may be atlocated at the rear focal plane of the second lens 124. Duringoperation, the SLM 110 rapidly displays elemental holograms 111 that aresynchronized to the 2D scanner 130 (and also to the SLM image location).The scanner 130 is adapted and controlled to spatially tile multiple SLMimages 111 behind a lenslet array 135 and large transform lens 140,which act to angularly tile the rapid sequence of elemental holograms111 generated by the SLM 110 into a super hologram 150.

The system 100 may be operated to create a dynamic hologram 150 that is,for example, a few inches on a side (e.g., 3 inches by 2.25 inches inone working prototype) with a +/−8 degrees by +/−1 degree field of viewand a frame rate of about 25 fps. Note, for a modestly sized displaywith only a few simultaneous viewers, horizontal parallax and field ofview (e.g., +/−8 degrees) are generally more important for obtaining anacceptable viewing experience (displayed 3D image) than verticalparallax and field of view (+/−1 degree) since a viewer's eyes and theviewers themselves are typically distributed horizontally relative tothe display system 100.

Challenges begin to arise, though, when even a modestly sized display isto be viewed by multiple viewers. In this case, it is preferable or evenrequired that the display system be scaled to provide a larger outputimage or display output. To this end, it may be desirable and/or usefulto combine multiple SLMs together behind a single coarse integraloptical system so as to create a display with a larger size and field ofview. Unfortunately, the current scanning and optical systems that areavailable to create the holographic image are larger than theholographic image itself. This problem makes tiling of multiple scanningsystems together behind the same coarse integral optic system difficultas large gaps are typically present in the viewing angle.

This problem of combining CIH displays is shown visually with the system200 of FIG. 2. As shown, a number of components of the CIH display 100have been provided in subsystem or subassembly 210. Likewise, a secondsubsystem 250 is stacked onto the subsystem 210. This subsystem 250includes an SLM 252 and an optical relay (e.g., a 4f relay) 254 withfirst and second lens 256 and 258, respectively. The CIH displaysubsystem 250 includes a scanner 260 disposed between the first andsecond lenses 256, 258 such as at the optical relay's Fourier plane. TheSLM 252 may be located at the front focal plan of the first lens 256,and the scanner 260 may be located at the rear focal plane of the firstlens 256 and at the front focal plane of the second lens 258. Thescanned and translated SLM image 263 may be at located at the rear focalplane of the second lens 258. During operation, the SLM 252 rapidlydisplays elemental holograms 253 that are synchronized to the 2D scanner260 (and also to the SLM image location).

The system 200 further includes a common transform lens 280 (larger thanlens 140 of display 100 of FIG. 1). The scanners 130 and 260 are adaptedand controlled to spatially tile multiple SLM images 111 and 253 behindlenslet arrays 135, 270 and large transform lens 280, which act toangularly tile the rapid sequence of elemental holograms 111, 253generated by the SLMs 110, 252 into a super hologram 290. Because theSLM image 263 is smaller than the lens 258 and further because the SLMimage 133 is smaller than the lens 124 n the subsystems 210, 250, thereis a physical gap, d_(gap), between the two lenslet arrays 135 and 170.Due in part to the gap 275, large gaps 292 and 294 are typically andundesirably present in the viewing angle of the hologram 290 (e.g., thephysical gap between the lenslet arrays puts a viewing gap into theimage).

Even if a display system is scalable, there eventually will be a limitin the size or expense of available or custom lenses or components. Forexample, the weight and cost of a lens goes roughly as the diametercubed. Further, the overall size of the system and interconnects willlikely become too cumbersome. At this point, then, it may be preferableand economical to create multiple identical but modestly sizedholographic display systems and then spatially tile them together tocreate a larger display.

However, similar to the scaling issues discussed above, it is difficultto tile many modestly sized displays together to form a large display.This difficulty arises, in part, because currently the system to createthe holographic display is larger than the holographic image. So, thereare large image gaps where the displays meet. This problem is shown inFIG. 3 with a tile CIH system 300 that is formed by tiling subsystems210, 250 each with their own transform lens 382, 384 (with side-by-sidetransform lenses 382, 384 providing a transform lens assembly 380). Thisproduces a pair of super holograms 390, 391 that are spaced apart, whichundesirably creates an image gap 395 readily observable by viewers ofthe system 300. Note, subsystems 210 and 250 could be scaled systemswith multiple scanners, SLMs, lenslet arrays, and common transformlenses.

With the goal of a scalable and tileable holographic display and theabove design challenges in mind, it may now be useful to analyze anddescribe a number of potentially useful and desirable solutions. To makea scalable and tileable display system, the display system preferably ismade to be the same size (or less) than the final image. In the displaysystem 100 of FIG. 1, a scanner 130 tiles multiple images 111 of the SLM110 behind the coarse integral optics (e.g., elements 120, 130, 135, and140). Both the scanner and coarse integral optics use variations ofrelay optics, with the scanner being at the Fourier plane of a relaypair and the coarse integral optics being similar to an array of relayoptics with a common final optic. As shown in FIG. 4, standard relayoptics 400 may use a pair of relay lenses 410, 420 to display an image430 of an object 440. As shown, the final lens 420 is larger than thescanned image 430 (i.e., H_(image)<H_(Lens 420)) because lens 420 mustcollect and redirect off-axis views toward the image 430.

One solution identified by the inventor is to use a different form ofrelay optics. FIG. 5 illustrates relay optics 500 that are configured inthe form of a periscope relay, which is a relay system with the smallesttube diameter. Periscope optics 500, as shown, use a field lens 520 toredirect the largest angle of an object 510 parallel to the tube. Theperiscope optics 500 further use a central relay lens 530 to transferthe image to the other end of the tube. A final large field lens 540 isused to make the system's field of view (fov) symmetric for the image550. The periscope optics 500 may have to be modified to work with acoarse integral array and with a scanner as well as to magnify the image550 (e.g., the image 550 has a height or size that matches that of therelay lens 530).

To this end, FIG. 6 illustrates a periscopic coarse integral arraydisplay 600 of the present description. In the display 600, there is anarray 610 of SLMs 612, 614, 616 (e.g., DMD micro-displays) stackedend-to-end with a height, H_(SLMS). The display 600 further includes afield lens array 620 associated with the SLM array 610 with a field lens622, 624, 626 paired with or provided for each of the SLMs 612, 614,616. The display 600 provides a stack or combined array of periscoperelay optics, and, to this end, the display 600 includes a relay lensarray 630 with a relay lens 632, 634, 636 associated with or paired withthe SLM/field lens pairs 612 and 622, 614 and 624, and 616 and 626. Thearray 630 has a height, H_(RL), that is equal to the height, H_(SLMS),of the SLM array 610. A common large transform lens 640 (with a height,H_(TL), matching the height, H_(RL), of the relay lens array 630) ispositioned between the relay lens array 630 and a second/final largefield lens 650, which is associated with image display/output and has aheight, H_(FL), equal to the height, H_(SLMS), of the SLM array 610.

The periscopic optic arrays (three shown in display 600 of FIG. 6 formedfrom the field lenses 622, 624, 626 plus the relay lenses 632, 634, 636)keep the rays from each SLM 612, 614, 616 confined to their bundles.Then, the large transform lens 640, which may be positioned in thedisplay 600 to be in contact with the relay lens array 630, redirectsand combines the outputs of the periscopic optic arrays so that theseoutputs overlap into a final hologram that is the size, H_(RL), of therelay lens array 630 (which is also equal to the height, H_(SLMS), ofthe SLM array 610) (i.e., H_(FL)=H_(RL)=H_(SLMS)) and their fields ofview (fovs) tile. A final field lens 650 is provided at the hologramplane (where the hologram is displayed by display system 600) and actsto bend the output views to make the field of view (fov) symmetric aboutthe optical axis.

The hologram provided by display 600 at lens 650 has a fixed image size,and the field of view of the final hologram is the same as the field ofview of any one of the SLMs 612, 614, 616. So, the display 600 is usefulfor creating a much larger hologram than hologram image 550 provide bydisplay 500 (e.g., with a height equal to the combined height, H_(SLMS),of the SLMs 612, 614, 616), but the display 600 still only provides asmall fov. For example, it may be desirable to provide a hologram ordisplayed image with a 30-degree field of view (fov), but each SLM 612,614, 616 and, therefore, the hologram of display 600 may only have a2-degree field of view (fov).

As shown in FIG. 1 with display system 100, a single high-speed SLM 110may be scanned using a scanner 130 at the Fourier plane of a relaysystem to provide an array of SLM images. The inventor recognized thatthis concept may be combined with the use of periscopic relay optics toprovide a periscopic scanning relay 700 as shown in FIG. 7, which isoperable to provide an array of SLM images, which may be provided behinda periscopic coarse integral array rather than requiring use of a stackor array of SLMs as shown in FIG. 6.

The periscopic scanning relay 700 is configured to be similar infunction to a periscopic relay in that it confines the ray bundles ofimages from the single SLM to a minimum tube diameter, which matches theperiscopic coarse integral relay's diameter (e.g., the height of thefield lenslet array 740). As shown for relay 700 in FIG. 7, a single SLM710 has an attached field lens 720. A mirror scanner 730 is included inthe relay 700 and positioned at the Fourier plane of the field lens 720.During operation, the SLM 710 rapidly displays elemental holograms 733that are synchronized to the 2D scanner 730 (and also to the SLM imagelocation). A large transform lens 724 reimages the SLM at the imageplane shown as SLM image array 750 in FIG. 7. The large transform lens724 changes the scanner rotation into an SLM image translation. An array740 of field lenslets 742, 744, 746 makes the field of view (fov) ofeach of the scanned SLM images in array 750 symmetric about the opticalaxis.

FIG. 8 illustrates a scanning periscopic coarse integral holographicdisplay 800 in which the periscopic scanning relay 700 is providedbehind a periscopic integral array, which is formed of: (a) a field lensarray 810 of lenses 812, 814, 816 paired with lenses 742, 744, 746 ofthe array 740 of the scanning relay; (b) a relay lens array 820including lenses 822, 824, 826 associated with lenses 812, 814, 816,respectively to provide a periscopic relay; (c) a common large transformlens 830 proximate to or contacting the array 820; and (d) a large fieldlens 840 at the hologram image plane. In the display 800, the array ofSLM images 733 from SLM 710 and scanner 730 appears directly behind theperiscopic coarse integral array and its components.

The periscopic coarse integral array optics creates a holographic imagethe size of the array optics (e.g., equal to the height of the fieldlens 840 which is equal to the height of transform lens 830 which, inturn, is equal to the height of the lens arrays 810 and 820) and withthe same field of view (fov) as any one of the SLM images from SLM 710.However, the SLM 710 may have a field of view (fov) that is less than 1degree. Hence, the scanning system 700 preferably also is configured todemagnify the SLM 710, such as by properly choosing the scanning relay'sfocal lengths, so its images have a desired field of view (fov) of thefinal hologram.

As shown in FIG. 9, the concepts taught in FIGS. 7 and 8 can be scaledto provide a display system 900 using two or more SLMs (image sources)with matching field and relay lenses behind common transform and fieldlenses. Particularly, the display system 900 includes a pair ofperiscopic scanning relays 700 and 700A that include components and thatoperates as discussed above with reference to FIGS. 7 and 8. Thescanning relays 700 and 700A are provided behind a pair of periscopicintegral arrays, which are formed of: (a) field lens arrays 810 and 810Awith lenses 812, 814, 816 paired with lenses 742, 744, 746 of the array740 of the scanning relay 700 and with lenses 812A, 814A, 816A pairedwith lenses 742A, 744A, 746A of the scanning relay 700A and (b) relaylens arrays 820 and 820A including lenses 822, 824, 826 associated withlenses 812, 814, 816, respectively to provide a first periscopic relayand including lenses 822A, 824A, 826A associated with lenses 812A, 814A,816A to provide a second periscopic relay.

The scaling of a scanning periscopic CIH display is achieved, in part,in display system 900 by providing a common large transform lens 930 (inplace of lens 830 in system 800) proximate to or contacting the twoarrays 820 and 820A and also by providing a large field lens 940 at thehologram image plane. In the display 900, the array of SLM images 733and 733A from SLMs 710 and 710A and scanners 730 and 730A appearsdirectly behind the periscopic coarse integral arrays and theircomponents.

As shown in FIG. 10, the concepts taught in FIGS. 7 and 8 can also beseamlessly tiled to provide a display system 900 using two, three, ormore SLMs (image sources) with matching field and relay lenses behindcommon transform and field lenses. Particularly, the display system 1000includes a three periscopic scanning relays 700, 700A, and 700B thatinclude components and that operates as discussed above with referenceto FIGS. 7 and 8. The scanning relays 700, 700A, and 700B are providedbehind three periscopic integral arrays, which are formed of: (a) fieldlens arrays 810, 810A, 810B with lenses 812, 814, 816 paired with lenses742, 744, 746 of the array 740 of the scanning relay 700, with lenses812A, 814A, 816A paired with lenses 742A, 744A, 746A of the scanningrelay 700A, and with lenses 812B, 814B, 816B paired with lenses 742B,744B, 746B of the scanning relay 700B and (b) relay lens arrays 820,820A, 820B including lenses 822, 824, 826 associated with lenses 812,814, 816, respectively to provide a first periscopic relay, includinglenses 822A, 824A, 826A associated with lenses 812A, 814A, 816A toprovide a second periscopic relay, and including lenses 822B, 824B, 826Bassociated with lenses 812B, 814B, 816B to provide a third periscopicrelay in display system 1000.

The tiling of a scanning periscopic CIH display is achieved, in part, indisplay system 1000 by providing an array 1030 of transform lensesincluding common large transform lens 1032 proximate to or contactingthe array 820B, common large transform lens 1034 proximate to orcontacting the array 820A, and common large transform lens 1036proximate to or contacting the array 820. Further, tiling is achieved indisplay system by providing an array 1040 of large field lenses 1042,1044, 1046 at the plane for the hologram image(s). In the display 1000,the array of SLM images 733, 733A, 733B from SLMs 710, 710A, 710B andscanners 730, 730A, 730B appears directly behind the periscopic coarseintegral arrays and their components.

Note, the above display systems are described for use in providing superholograms. However, it will be understood that other images may beprovided by the SLMs or other image sources provided behind coarseintegral optics. For example, a two-dimensional (2D) multi-view versionof a display system may be provided. In this version, elemental 2Dimages (display devices such as SLMs) are used to give a multi-viewimage instead of holograms, and the display system may be adapted toprovide scanning of 2D images to get 3D images as output from the coarseintegral optics, with the scaling and tiling problems handled asdescribed herein.

The SLMs used in the described display systems may take the form ofdigital mirror devices (DMDs), liquid crystal on silicon (LCOS) devices,optically addressed SLMs (OASLMs), electrically addressed SLMs (EASLMs),or the like. These may each be operated to output an elemental hologram,and these are combined by a coarse integral optical assembly. In somecases, the spacing of the elemental images should be equal to thelenslet width or height to ensure the tiled view zones abut without gapsor overlap. The size of the super hologram may be stated as D=f₂/f₁ d,where f₂ is the focal length of the large transform lens. The field ofview in one direction of the super hologram is Φ_(x,y)=n_(x,y)·f₁/f₂·θ,where n_(x) or n_(y) is the number of elemental images in thatdirection. The number of elemental images (i.e., number of SLMs in thearray) can be selected to be different in the horizontal and verticaldirections (i.e., n_(x) does not have to equal n_(y)), which can be usedto provide different fields of view for a hologram. The resultinghologram may be further demagnified to decrease its image size andincrease its field of view (or vice versa) in particular implementationsof the system.

A coarse integral holographic display can be used to generateholographic images or super holograms that exhibit full parallax withdifferent fields of view in the horizontal and vertical directions. Thesuper hologram also exhibits accommodation, occlusion, andview-dependent shading. The holographic image may appear to the viewerto be a real image floating in front of or behind the display (e.g., infront of the final field lens).

Based on the inventor's design, it is believed that course integralholographic displays can be built or manufactured to effectively usecoarse integral optics. These optics or optical assemblies will allowoutput images from multiple SLMs to be combined efficiently, which willincrease the holographic display's space-bandwidth product (e.g.,information capacity). The space-bandwidth product can be flexiblyassigned such as more to the horizontal field of view than the verticalfield of view. Furthermore, the field of view can be asymmetric, whichcan be useful in displays that may be normally or often viewed off axis,such as table displays.

Although many SLMs have coarse pitches over small areas, many SLMs arecapable of high bandwidth and frame rates, e.g., DMDs are capable ofseveral thousand binary frames per second. Only 15 to 60 frames persecond are needed for apparent continuous motion. The additionalbandwidth/frames per second can be used to sequentially create multipleelemental holograms with a single SLM, which can then be spatially tiledbehind the lens array using 2D scanners and then angularly tiled usingthe coarse integral optics. The SLM temporally multiplexes the elementalholograms, the 2D scanner spatially multiplexes the elemental holograms,and the coarse integral optics angularly multiplexes the elementalholograms.

The scanning system may include an SLM, a 4f optical relay, and ascanner located at the optical relay's Fourier plane. The SLM is locatedat the front focal plane of the first lens. The scanner is located atthe rear focal plane of the first lens and also the front focal plane ofthe second lens (scanning on the Fourier plane). The scanned andtranslated SLM image is located at the rear focal plane of the secondlens. The SLM rapidly displays elemental holograms (computed to displayholographic images from the appropriate viewpoints) that aresynchronized to the 2D scanner and SLM image location. To tile the SLMimage without motion blur caused by scanning, the SLM illumination canbe flashed when the scanner and SLM image are at the tile locations. Thescanner spatially tiles multiple SLM images behind the lenslet array. Aswith other configurations, a large transform lens is provided forangularly tiling the rapid sequence of elemental holograms generated bythe single SLM into a super hologram.

The display systems taught herein may be thought of as providing angulartiling with their coarse integral optics. Such angular tiling hasadvantages over spatial tiling of SLMs. With spatial tiling, there arenoticeable seams in the generated or output holographic image due togaps between the SLMs from the borders and electronics. Gaps andmisalignments in the spatial tiling appear at the hologram plane andvisually interfere with and confuse the 3D imagery.

In contrast, with angular tiling as provided by the displays of thepresent description, the seams appear as gaps in the angular views.Small missing view zones are visually less obtrusive and can further beblended using a light diffuser (not shown in FIG. 1 but readilyunderstood by those skilled in the art). Angular misalignments result indisjointed motion parallax. The angular tiling also lends itself toview-dependent holographic rendering algorithms, such as holographicstereogram and diffraction specific parallax panoramagrams. Further,view-dependent holographic algorithms naturally handle view-dependentlighting and shading, occlusion, and accommodation cues in theholographic images.

With the above description in mind, it may be useful to explain some ofthese concepts again and/or in more detail to clarify how one mayimplement a holographic display by combining multiple spatial lightmodulators to achieve a larger holographic output or 3D displayed imagewhile providing at least some amount of vertical parallax. The proposedsolution or display system combines holographic displays with coarseintegral displays. The holographic displays (e.g., an array of SLMs)provide a set or array of fully 3D images (e.g., elemental holograms)but with a small area and a low fov. Each of these small holograms is adifferent (narrow) viewpoint of the same 3D scene. The coarse integraldisplay (or coarse integral optical assembly or optics) combines themultiple narrow field of view holograms into a single large (in size andfov) hologram or “super hologram.”

Although the invention has been described and illustrated with a certaindegree of particularity, it is understood that the present disclosurehas been made only by way of example, and that numerous changes in thecombination and arrangement of parts can be resorted to by those skilledin the art without departing from the spirit and scope of the invention,as hereinafter claimed.

The display systems described provide a number of advantages overexisting systems. Existing display systems attempting to achieve similarresults are very expensive (e.g., about $100,000 per 5-inch holographicbrick), and this expense is in part due to the use of a ferroelectricshutter array and the use of an OASLM. Tiling may be possible with sucha system but it would be prohibitively expensive. Scanning onto anerasable photopolymer presently can only be performed on a 6-inch by6-inch frame every two seconds, which is much too slow for mostapplications. Newer screens that use erasable liquid crystal screens arecapable of refreshing faster, but they do not have an actual scanningholographic display system to distribute the SLM images onto the screen.

In contrast, the scanning periscopic coarse integral holographic displayis scalable (in that it can use multiple SLMs and scanners to increaseits size and field of view) and is tileable (in that multiple completesystems can be placed next to each other to increase the size of thedisplay). The system does not need a screen to store the holographicimage while the hologram is built up, although it can be used with sucha screen (e.g., an OASLM, erasable photopolymer, or other recordablephotographic media) to make either a dynamic display or even aholographic printer.

The periscopic scanning coarse integral holographic display builds uponthe scanning coarse integral holographic display. A scanning CIH displayhas been constructed and has proven the concepts described herein. It islikely that an optimized CIH system will be able to achieve a 3-inch by2.25-inch hologram with +/−8 degrees by +/−1 degree fov at 25 fps from asingle digital micro mirror (DMD) SLM and single scanner. The change tothe periscopic scanning coarse integral optics is likely useful forkeeping the same achievable size from a single SLM, and it should bescalable to multiple scanners and SLMs and tileable to multiple CIHdisplay systems. The scanning periscopic coarse integral holographicdisplay becomes a “holographic brick” that one can use to modularlyconstruct a holographic display of any size, such as to build aholographic wall.

I claim:
 1. A holographic display system, comprising: an array ofholographic display devices operable to provide a plurality ofholographic images of a scene from differing viewpoints of the scene;and a periscopic coarse integral optics assembly positioned between thearray of holographic display devices and a viewing space for theholographic display system, wherein the periscopic coarse integraloptics assembly includes a periscopic relay for each of the holographicdisplay devices to relay the holographic images and wherein theperiscopic coarse integral optics assembly is adapted to combine theplurality of holographic images into a single hologram viewable in ahologram image plane.
 2. The system of claim 1, wherein the holographicdisplay devices each comprises a spatial light modulator operable todisplay one of the plurality of holographic images.
 3. The system ofclaim 1, wherein the periscopic relay comprises a field lens adjacent anoutput surface of a corresponding one of the holographic display devicesand further comprises a relay lens spaced apart from each of the fieldlenses.
 4. The system of claim 3, wherein the periscopic coarse integraloptics assembly further includes a common transform lens proximate tothe relay lenses combining the plurality of holographic imagestransmitted from the relay lenses.
 5. The system of claim 4, wherein theperiscopic coarse integral optics assembly further includes a field lensat the hologram image plane.
 6. The system of claim 5, wherein the fieldlens has a height substantially equal to the height of the commontransform lens.
 7. The system of claim 6, wherein the common transformlens has a height substantially equal to the height of the array ofholographic display devices.
 8. A scanning periscopic coarse integralholographic display, comprising: a scanning relay comprising a spatiallight modulator providing elemental holograms of a 3D scene, an array offield lenslets, and a scanner operable to direct each of the elementalholograms onto one of the field lenslets; and a periscopic coarseintegral optics assembly positioned between the scanning relay and aviewing space for the holographic display, wherein the periscopic coarseintegral optics assembly includes a periscopic relay for each of thefield lenslets to relay the elemental holograms and wherein theperiscopic coarse integral optics assembly is adapted to combine theplurality of holographic images into a single hologram viewable in ahologram image plane.
 9. The holographic display of claim 8, wherein theperiscopic relay comprises a field lens adjacent an output surface of acorresponding one of the field lenslets of the scanning relay andfurther comprises a relay lens spaced apart from each of the fieldlenses of the periscopic relay.
 10. The holographic display of claim 9,wherein the periscopic coarse integral optics assembly further includesa common transform lens proximate to the relay lenses combining theplurality of holographic images transmitted from the relay lenses. 11.The holographic display of claim 10, wherein the periscopic coarseintegral optics assembly further includes a field lens at the hologramimage plane.
 12. The holographic display of claim 11, wherein the fieldlens has a height substantially equal to the height of the commontransform lens.
 13. The holographic display of claim 12, wherein thecommon transform lens has a height substantially equal to the height ofthe array of field lenslets in the scanning relay.
 14. A displayassembly, comprising: at least two scanning relays each comprising: aspatial light modulator providing elemental holograms or 2D elementalimages; an array of field lenslets; and a scanner operable to directeach of the elemental holograms or the 2D elemental images onto one ofthe field lenslets; and a periscopic coarse integral optics assemblyincluding a periscopic relay for each of the field lenslets, whereineach of the periscopic relays comprises a field lens adjacent an outputsurface of a corresponding one of the field lenslets and furthercomprises a relay lens spaced apart from each of the field lenses of theperiscopic relay.
 15. The assembly of claim 14, wherein the periscopiccoarse integral optics assembly further includes a common transform lensproximate to the relay lenses combining the elemental holograms or the2D elemental images transmitted from the relay lenses.
 16. The assemblyof claim 15, wherein the periscopic coarse integral optics assemblyfurther includes a field lens at a hologram or tiled 2D image plane forthe assembly.
 17. The assembly of claim 16, wherein the field lens has aheight substantially equal to the height of the common transform lens.18. The assembly of claim 14, wherein the periscopic coarse integraloptics assembly further includes a transform lens proximate to the relaylenses associated with each of the scanning relays that combines theelemental holograms or the 2D elemental images transmitted from therelay lenses of each of the scanning relay.
 19. The assembly of claim18, wherein the periscopic coarse integral optics assembly furtherincludes a field lens at the superhologram or 3D multiview image plane,paired with each of the transform lenses.
 20. The assembly of claim 19,wherein the field lenses each has a height substantially equal to theheight of a corresponding one of the transform lenses.